While this section provides background information related to the present disclosure, the material discussed in this section is not necessarily prior art.
The design and manufacture of a structure requires the selection of appropriate materials for structural components or device substructures. To select a suitable material, scientists, engineers, designers, architects, etc., require specific knowledge of the material such as the internal stress and strain patterns and responses the material exhibits when a force is applied. Various measurement devices have been developed for testing, inspecting, measuring, and quantifying the physical properties of materials that are under load or after loading when no load is applied. Further, the characterization of material properties during loading is known as “in situ” testing or “in situ” inspection. For example, X-rays, acoustic waves, etc., may be used to perform measurements on a sample during the application of a load using computed tomography, radiography, and other well-known inspection techniques.
A test sample may be secured in place during a measurement using a mechanical load frame (i.e., a test fixture) that exerts a load (e.g., tensile force, compressive force, a shear force, or a combination thereof via uniaxial, biaxial, etc., type fixturing) on the test sample. Additionally, thermal or moisture gradients may be applied to a test sample, for example a “coupon,” to induce deformation of the coupon by imparting stress/strain gradients to the coupon while it is gripped by and within a load frame. Combinations of thermal and mechanical loadings may also occur. The load frame may include electric motors and/or hydraulics to exert the load on the test sample.
Currently, computed tomography, standard radiography inspection, and other measurement techniques are able to capture constituent (e.g., fiber and matrix) damage modes in composites when a load such as a tensile force is applied to a test sample by a load frame. This is also the case for varieties of composite materials (short fiber, continuous, etc.), thermoplastics, thermosets, additive manufactured materials, metal alloys, etc. Commercially available load frames include benchtop designs as well as larger systems. However, the testing capability of benchtop options is limited, with low load capability (e.g., less than 2 kips) resulting from, for example, small load cell capacity, the size/machine footprint, and at least in part from a limited driving voltage. This low load limitation requires testing of thin test samples which reduces the available range of test sample configurations, material types, and testing conditions. For example, thicker test samples, samples with notches, and samples of various ply layups where the strength exceeds the loading capability are not measurable to the near failure level using these systems because the load level required is beyond the system capability. Larger systems that provide higher load capability may not be portable as they may be fixed in place, and may require extensive and expensive redesign for different sizes and shapes of the test samples. Both benchtop and larger systems have a relatively high cost, and are generally dedicated to only one type of measurement. Switching between measurement techniques, for example, between computed tomography and radiology measurements, as well as measuring a test sample under varying or extreme environmental conditions, is expensive or not possible. Characterization measurements of a material using test samples may be subcontracted to external host sites, but subcontracting may be expensive and requires long initial lead times and increased time to complete testing.
A load frame that is portable, simply reconfigurable and adjustable for various test sample (i.e., coupon) sizes, and able to integrate with different types of metrology systems, such as computed tomography, acoustic emission, and radiology systems, would be a welcome addition to the art.